This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The goal of this project is to understand the genetic variation in the common marmoset non-human primate model organism. The marmoset is often used as an alternative to old world monkeys because of its smaller size, faster reproductive cycle and husbandry. Unlike rodent model organisms but similar to rhesus macaques, marmosets are outbred and vary genetically from one another. We have pioneered the use of naturally-occurring genetic variation in rhesus macaques as a model of human neuropsychiatric disease. This work in marmosets and new world monkey expands upon these efforts, allowing for modeling in additional model organisms. This, in turn, allows for a comparison across species to better understand the directionality and evolution of the observed genetic and phenotypic traits. Further, marmosets (and callitrichids more generally) have long been noted to be blood chimeras;more recently this chimerism has been observed in other tissues as well. Callitrichids nearly always produce fraternal twins which exchange genetic material in utero. Despite this chimerism, no gross phenotypes are observed, even among XX females harboring their male siblings Y chromosome as well. Understanding this phenomena not only will help in understanding in utero development in primates, but also may aid in developing novel strategies to ameliorate rejection following organ transplantation.